1. Field of the Invention
The present invention relates to washing apparatus and method for scrubbing substrates such as semiconductor wafers by brushes and, more particularly, device and method for turning the substrates upside down or vice versa to scrub both surfaces of substrate.
2. Description of the Related Art
Various kinds of micro-process are added to substrates (such as semiconductor wafers and LCD substrates) in the course of manufacturing semiconductor devices, providing that the face surface of each substrate be already made clean. Each substrate, therefore, must be made clean on the face surface thereof before and between the micro-processes added. The face surface of each substrate is scrubbed (or brush-washed) by a scrubber prior to coating it with resist in the case of the photolithography, for example. When particles adhere to a reverse surface of the substrate, an excellent pattern cannot be formed on the face surface of the substrate when it is to be exposed, because it is held tilted. It is therefore usual to scrub both surfaces of the substrate.
Scrubbers of two types have been employed in the course of manufacturing semiconductor devices. One of them is the single side type scrubber intended to scrub only the single side of each substrate, and the other is the both-side type scrubber intended to scrub both surfaces of substrate at the same time. In the case of the single side type scrubber, the face surface of substrate is scrubbed by the brush, while rotating the substrate held on a spin chuck, to wash it clean with washing solution. In the case of the both-side type scrubber, the face surface and the reverse surface of substrate are scrubbed by brushes to wash them clean.
The single side scrubber has been used by the process of washing only the face surface of substrate and the both-side type scrubber by the process, such as the photolithography, of scrubbing the reverse surface of substrate as well as the face surface thereof. The both-side type scrubber, however, is intended to press the brushes against both surfaces of substrate and supply washing solution to them, while rotating the substrate. This makes the both-side type scrubber complicate and its cost high.
In order to solve these disadvantages of the conventional scrubbers, there has been provided a scrubber used as both for scrubbing the single-side and both-side. A pair of arms for turning substrates upside down or vice versa are arranged adjacent to spin chucks of the single- and both-side type scrubbers to enable the face surface and the reverse surface of substrate to be selectively or alternately scrubbed. In the case of this single- and both-side type scrubber, the arms pick up the substrate (or semiconductor wafer) from the spin chuck after the face surface of the substrate is scrubbed, turn it upside down at a position remote from the spin chuck, and transfer it onto the spin chuck. The face surface of substrate as well as the reverse surface thereof can be thus scrubbed by a single brush. In addition, the arms include the orientation flat aligning mechanism and the orientation flat of each substrate supported by the arms can be therefore aligned with a desired direction or position.
In the case of this single- and both-side type scrubber, however, one pair of arms conduct three functions for carrying-in and -out substrate, for turning substrate so as to vice versa, and for aligning its orientation flat with the predetermined direction or position. This makes the arm drive mechanism complicated in structure and the apparatus itself large in size accordingly. The face surface of substrate is scrubbed and, turning step and orientation flat aligning step must be carried out before the reverse surface of substrate is scrubbed. This makes the throughput of the washing process low.
Further, various kinds of drive means in each unit are susceptible to erosion, and excessive load is added to the drive motor. This leads the apparatus to malfuction.